The present invention relates to a slip anchor for a seat belt, which is movably supported on pillar or the like of a car body and slidably guides the webbing of seat belt in a longitudinal direction.
The seat belt unit to be provided on a seat of a vehicle such as an automobile restrains the occupant of the vehicle in an emergency such as vehicle collision and protects the occupant from injury due to crash against car body.
Such seat belt is furnished with a slip anchor, which is supported on a pillar or the like of a car body and slidably guides the webbing of seat belt in a longitudinal direction. By this slip anchor, it is possible to restrain the occupant by seat belt at correct position.
If webbing is twisted, webbing is not only not correctly adapted to the occupant, but smooth movement of the webbing is also hindered. Therefore, when webbing is guided by slip anchor, webbing must not be twisted.
In the past, a slip anchor with means for preventing the twisting of webbing has been known as, for example, the one disclosed in the Japanese Provisional Utility Model Publication No. 52-148622. As shown in FIG. 2(a), the slip anchor disclosed in this publication is provided with a main unit 1, comprising a mount 2 and a guide unit 3. The main unit 1 is movably mounted on car body by adequate fixing means such as bolt, which is inserted into a mounting hole 4 of the mount 2. The guide unit 3 is furnished with a guide hole 5, into which the webbing 6 of seat belt is passed. The gap "a" of the webbing 6 in the direction of its thickness formed by the guide hole 5 is set to such size that the webbing 6 is not pulled in twisted state.
According to the slip anchor for seat belt as described above, the webbing 6 is not guided in twisted state and it smoothly slides in the guide hole 5 at all times.
In such slip anchor, it is desirable that the webbing 6 naturally and smoothly slides in a lateral direction when it is pulled. For this reason, a slip anchor of conventional type is furnished with escape portions 5a on both ends of the guide hole 5. In this case, the escape portion 5a is formed in curve on the mount 2 so that the gap "b" is formed in the same size as the gap "a" of the guide hole 5. By this escape portion 5a, the webbing 6 can be smoothly displaced when it is pulled.
However, because the gap "b" of the escape portion 5a in this slip anchor is in the same size as the above gap "a", the lateral portion 6a of the webbing 6 is brought into touch with the end 5a' of the escape portion 5a when the webbing 6 is moved, and the surface of the lateral portion 6a of the webbing 6 may be damaged. To avoid the contact between the lateral portion 6a of the webbing 6 and the end 5a' of the escape portion 5a, it has been proposed to form the escape portion 5b wider as shown in FIG. 2(b). In such slip anchor, the escape portion 5b is big and there is no end, with which the lateral portion 6a of the webbing is brought into contact.
However, because the escape portion 5b is big in the slip anchor shown in FIG. 2(b), the webbing 6 may be twisted in some cases as shown in FIG. 3. Accordingly, it is not possible to form the escape portion 5b unconditionally.